1. Field of the Invention
The disclosure relates generally to systems and methods for communicating between components of a networked fire alarm system, and more particularly to a system and method for providing emergency alarm signaling when TCP/IP communication failures occur in a networked fire alarm system.
2. Discussion of Related Art
Alarm systems, such as fire alarm and security systems, typically include one or more centralized fire panels that receive information from various sensors that are distributed throughout a structure or area. For example, referring to FIG. 1, a typical fire alarm system 10 may include a plurality of initiating devices 12 (e.g. smoke detectors, manually-actuated pull stations, etc.) that are connected to one or more fire panels 14. During normal operation of the alarm system 10, the fire panel 14 may monitor electrical signals associated with each of the initiating devices 12 for variations that may represent the occurrence of an alarm condition. For example, a variation in a particular electrical signal may represent the detection of smoke by a smoke detector in a corresponding area, or “zone,” of a building in which the smoke detector is located, and may cause the fire panel 14 to enter an alarm mode. The fire panel 14 may be configured to respond to such a condition by initiating certain predefined actions, such as activating one or more notification appliances 16 (e.g. strobes, sirens, public announcement systems, etc.) within the monitored building.
The exemplary alarm system 10 may also include a workstation 18, such as a personal computer (PC) a link to a central station or server, which is operatively connected to the fire panel 14 of the alarm system 10. For monitoring applications that involve a large number of buildings, such as a college campuses or commercial campuses, each of the buildings on the campus may have its own fire panel 14. It is often desirable in such applications to be able to monitor all of the fire panels 14 from a single site, and thus, the fire panels 14 may be part of a network, with the fire panels 14 and workstation 18 connected to the network as network nodes. In this way the workstation 18 can be located in one of the monitored buildings, or a separate building, and may be used to monitor the alarm status of all the initiating devices 12 located in all of the buildings via their respective fire panels. Although not shown, the system 10 may also include a connection to a remote central monitoring facility so that a third party monitoring service can monitor and react to alarms generated by the system.
In some cases, a network of fire panels can be built up as a redundant ring using a switch or network card in each panel to enable communication with adjacent panels. One requirement for fire panel networks is redundancy. For example, standards such as European standard “EN54—Fire Detection and Alarm Systems,” require that in case of failure it is not permissible to lose more than a certain number of initiating devices upon a first failure. For EN54 this number is 512 devices. As a result, a panel having more than, for example, 512 devices or support features for more than 512 devices requires redundancy. For networked fire panels this problem is currently solved using redundant network processors and a redundant network topology. In case of a Transmission Control Protocol/Internet Protocol (TCP/IP) based network, a ring topology or other redundant topology can be built by using a TCP/IP switch or router in every fire panel which supports two redundant connections to the switch. As a result, however, the switch/router, and in some cases the network processor, represent a single point of failure. That is, if the switch/router and/or network processor fail, the fire panel is unable to process and transmit alarm signals triggered by the initiating devices coupled to that panel. This single point of failure can be avoided by using multiple switches/routers and multiple network processors so that loss of a single switch/router or a single network processor would not impact successful transmission of alarm signals to adjacent panels and the workstation or a central monitoring station. It will be appreciated, however, that providing multiple switches/routers and/or multiple processors in each panel undesirably increases the cost and complexity of the overall network.